In this "ancillary only" study, the Mayo GCRC grant is supporting measurement of leptin concentrations in samples from the CARDIA study. Dr. Michael Jensen of the Mayo Clinic is core director of the Minnesota Obesity Center (University of Minnesota). Samples from the CARDIA study (a prospective cohort study to investigate factors that influence coronary heart disease risk factors during young adulthood) are ideal to address several questions related to leptin's role as a "lipostat" in man. This ancillary study was approved by the CARDIA review board. Samples are balanced on race and sex. Samples from 1000 African- Americans and 1000 whites will be analyzed.